Field of the Invention
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. For forming a desired circuit pattern on such semiconductor devices, a master or “original” pattern (also called a mask or a reticle) of high accuracy is needed. Thus, the electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for producing such a high-precision master pattern.
FIG. 8 is a conceptual diagram explaining operations of a variable shaping type electron beam writing or “drawing” apparatus. The variable shaping electron beam (EB) writing apparatus operates as described below. A first aperture plate 410 has a quadrangular aperture 411 for shaping an electron beam 330. A second aperture plate 420 has a variable shape aperture 421 for shaping the electron beam 330 having passed through the aperture 411 of the first aperture plate 410 into a desired quadrangular shape. The electron beam 330 emitted from a charged particle source 430 and having passed through the aperture 411 is deflected by a deflector to pass through a part of the variable shape aperture 421 of the second aperture plate 420, and thereby to irradiate a target object or “sample” 340 placed on a stage which continuously moves in one predetermined direction (e.g., the x direction) during the writing. In other words, a quadrangular shape that can pass through both the aperture 411 and the variable shape aperture 421 is used for pattern writing in a writing region of the target object 340 on the stage continuously moving in the x direction. This method of forming a given shape by letting beams pass through both the aperture 411 of the first aperture plate 410 and the variable shape aperture 421 of the second aperture plate 420 is referred to as a variable shaped beam (VSB) system.
In the variable shaped beam system, the shape and size of a beam is determined by firstly shaping the beam, for example, into a quadrangular beam by letting it pass through the first shaping aperture, and then adjusting the position of the quadrangular beam to be deflected to the opening of the second aperture. Therefore, the position of the beam after being shaped differs depending upon the figure type. Accordingly, for applying a beam after being shaped to a desired position on the mask, it is necessary to reverse the beams deflected to different positions for beam shaping. However, there is a limitation to the deflectable range to be deflected by a deflector. Therefore, when deflecting a shaped beam onto a mask, deviation of the deflectable region occurs depending upon the figure type even when the same deflector is used for deflection. The overlapped region where deflectable regions of figures are overlapped with each other is a region deflectable with respect to all the figure types. Since the deflection region deflectable by the deflector is limited to the region deflectable with respect to all the figure types, there is a problem in that the deflection region is small.
In order to cope with this problem, conventionally, it has been examined a method in which when generating shot data for each shot, correction is performed by moving the position on the shot data according to the figure type to be shaped (e.g., refer to Japanese Published Unexamined Application (JP-A) No. 2010-219482). However, this method needs to perform calculation processing for correcting the shot data itself. In the variable shaped beam system, it is difficult to write a figure pattern serving as a writing target at a time, and therefore, each figure pattern is divided into a plurality of shot figures each having a size that can be irradiated by one shot so as to combine them to write a desired figure pattern. Therefore, the number of a plurality of shot figures obtained by dividing a figure pattern is enormous. Then, shot data is generated for each of the enormous number of shot figures. Accordingly, when correcting the position on the shot data, since movement calculation processing of each position is performed for each shot, a new problem occurs in that the calculation processing time in generating shot data increases.
On the other hand, not regarding the variable shaped beam system but regarding a character projection system of the writing apparatus, there is disclosed a method of dividing a writing region into subfields and correcting the subfield origin position according to a character shape (e.g., refer to Japanese Published Unexamined Application (JP-A) No. 6-267834). However, if applying this method to the variable shaped beam system, another new problem occurs. Deflection speed of subfield deflection is, for example, ten times as slow as that of the shaping deflection. Therefore, if the operation (deflection operation) of moving the origin position of the subfield is performed in each shot, there is a problem that the throughput of writing processing decreases greatly.